1. Technical Field
The present disclosure relates to a power supply circuit for a CPU (central processing unit).
2. Description of Related Art
With progress in computer techniques, the number of working phases of power supply circuits for a CPU has increased from one to four or more. For example, INTEL VR12 has four operating modes, PS0, PS1, PS2 and PS3. In mode PS0, the power supply circuit for a CPU operates in all working phases simultaneously to provide more current to the CPU. The number of working phases on which the power supply circuit for a CPU operates decreases with increase in PS modes.
Generally, a power supply circuit supplies current to a CPU based on an operating mode signal sent to a Pulse-Width Modulator (PWM) from the CPU, enabling the power supply circuit to operate in an adequate number of working phases. The current in the entire circuit is the sum of each working phase. Hence, the amount of current increases with the number of working phases on which the power supply circuit operates. In addition, generally, a power supply circuit for a CPU has an excessive current prevention circuit merely for the PS0 mode (that is, the mode which enables CPU to operate in all working phases).
When operating abnormally, a CPU can output an operating mode signal which not corresponds to the operating mode of the CPU to the pulse width modulator. For instance, outputting an operating mode signal corresponding to operating mode PS1, PS2 or PS3 when the CPU operates in mode PS0. Consequently, when receiving the operating mode signal, the pulse width modulator decreases the number of working phases on which the power supply circuit operates to three phases, two phases or one phase while the CPU still operates in mode PS0. In other words, the amount of current in the power supply circuit for a CPU equals that when the CPU still operates in mode PS0 (that is, the sum of the currents on four working phases). As a result, the current of each phase is increased, and the MOSFET or other components in the power supply circuit may be damaged. In addition, the excessive current prevention circuit of the power supply circuit for a CPU merely operates when receiving an operating mode signal corresponding to operating mode PS0 from the CPU. In sum, there is room for improvement.